This disclosure relates to dispenser pumps, and particularly but not exclusively to dispenser pumps suitable for mass manufacture predominantly in plastics material.
Dispenser pumps of the general kind to which the disclosure relates have a pump chamber alterable in volume by the action of a reciprocable plunger. A pump chamber inlet which receives material from a supply container includes an inlet valve. The outlet through which the dispensed material leaves the pump chamber may have an outlet valve. There may be a projecting discharge spout or nozzle. Some of these options are requirements in certain aspects of this disclosure, as explained below.
Preferablyxe2x80x94and in some of the present proposals essentiallyxe2x80x94volume alteration of the pump chamber is by a piston operating slidably in a cylinder, e.g. a plunger piston operating in a fixed cylinder formed by the pump body, typically with an outward seal on the piston wiping the cylinder wall in use.
The present proposals are preferably embodied in pumps having the outlet (and spout/nozzle, where provided) fixed relative to the pump body but they may also be implemented in movable-nozzle pumps i.e. in which an outlet passage extends through the plunger.
In a first aspect our proposals have to do with the difficulty associated with product which remains in the discharge nozzle of the dispenser after the dispensing stroke. Particular difficulties, depending on the nature of the product, include dripping from the nozzle and nozzle blockage by dried product residues.
These difficulties are known and have been addressed in the prior art by what can generally be called suck-back arrangements whereby product residue is drawn back from the nozzle at the end of the dispensing stroke. See e.g. EP-A-779106 and our own WO-A-95/25600. These earlier proposals delay or compromise the closure of an outlet valve after dispensing so that the negative pressure in the pump chamber during priming can act to suck the residue in the nozzle back through the valve.
In a first aspect of our new proposals a dispenser pump of the kind described has a discharge passage extending along a discharge nozzle downstream of an outlet valve arrangement, the outlet valve arrangement including a blocking element movable along the discharge passage between a closed valve condition at an upstream position and an open valve condition at a downstream position. The blocking element is biased towards the upstream, closed position e.g by spring means and/or gravity. The valve arrangement defines a draw path in the discharge passage between the mentioned downstream and upstream positions, dimensioned to be substantially blocked by the blocking element. During the dispensing stroke the initial flow of pressurized product from the pump chamber carries the blocking element downstream against the mentioned bias to the open condition at the downstream position where the product can flow out past it. At the end of the dispensing stroke the blocking element is biased back from the open condition and along the draw path which it substantially blocks so that, as it travels back, product residue in the discharge passage region downstream of the outlet valve arrangement is drawn-back away from the nozzle tip.
This arrangement may reduce or prevent dripping at a downwardly-directed nozzle end opening, without relying on generating negative pressure in the pump chamber since material need not pass the valve""s blocking element. The arrangement is therefore specially useful for pumps having no means for biasing the plunger back to its extended position after the dispensing stroke, and/or in which the supply is disposed relative to the pump so as to give a prevailing positive pressure in through the inlet valve.
Preferably the nozzle is a fixed nozzle projecting sideways from the pump body. The preferred form has a portion extending upwardly from the outlet valve arrangementxe2x80x94enabling gravity biasingxe2x80x94leading to a downwardly-directed end opening.
The blocking element is preferably a single valve body movable along a valve body housing which provides a sealing seat for the body at the upstream end, an enclosed tubular conduit for the draw path in which the valve body is a relatively close fit (having regard however to the viscosity and other properties of the product so as to avoid sticking), preferably parallel-sided, and one or more flow openings providing for relatively free product flow around the valve body at the downstream end. The downstream end may also provide a retaining stop to limit movement of the valve body. Biasing means such as a spring may also be provided to act on the valve body, e.g. a compression spring disposed between the valve body and a downstream reaction abutment of the valve arrangement.
For products which are viscous and/or contain particulates the valve body preferably makes a sharp edge engagement with the sealing seat.
The valve body may be a simple rigid ball or other form of sliding solid plug. It may have a flexible peripheral sealing lip on a central body if closer sealing in the draw path is required; e.g. for lower viscosity liquids. One special novel form of sealing lip is a radial elastomeric flange e.g. provided by trapping an elastomer disc onto the end of a rigid valve body of smaller diameter. This may seal fluid while allowing particulates to pass.
The valve body may make an axial guide sliding engagement with adjacent fixed structure of the valve arrangement to maintain its axial orientation in the draw path.
The withdrawn residue volume depends on the cross-section and length of the draw path, and is determined with reference to the practical requirements e.g. the shape-and size of the nozzle. Preferably the length of travel of the blocking element while blocking the draw path is at least half and more preferably at least the same as the maximum transverse cross-sectional dimension of the blocking element.
A simple valve body is not the only possibility. For example the blocking element may be itself a sub-assembly comprising a valve body retained in a sleeve, the body being movable along the sleeve between a sealing seat and one or more flow openings for the above-described behaviours, and the sleeve itself being mobile along the discharge passage between upstream and downstream positions, blocking the passage whenever the valve body is against its sealing seat.
The suck-back mechanism proposed above moves product back into the pump chamber. This volume may be accommodated in various ways according to the nature of the pump. Where there is a plunger return spring, the suck-back volume joins the volume priming the pump chamber. If there is compliance or delay in the inlet valve and no back-pressure behind the inlet valve, material drawn back can escape that way. Or, it may be accommodated by a slight movement of the plunger.
However, for the particular case in which the above modes of accommodation are not available, unreliable or not desired we propose that the pump chamber may be provided with a yielding wall element to accommodate the drawn-back volume without requiring back-flow at the inlet or bodily movement of the plunger. It is also preferred that this accommodation is free, i.e. not against a resilience which would tend to urge the extra volume gradually out again past the outlet valve. To this end, the yielding wall element is preferably provided in accordance with the second set of proposals which follow.
In our second set of proposals, a dispenser pump of the kind described has a plunger which is a piston plunger making a sliding primary seal against a cylinder wall comprised in a body of the pump, and reciprocable in this pump body cylinder to alter the pump chamber volume. The piston plunger has a head, and a shaft which has an outer annular shaft element (e.g. a ring, sleeve or tube piston) to which the sliding primary seal is made and an end face directed inwardly onto the pump chamber. The end face has a central portion which by pressing on the plunger head is axially advanceable relative to the shaft""s outer annular shaft portion, against a restoring force, to a displacement position. On releasing the pressure on the plunger head it retracts axially relative to the outer annular portion, under the influence of the restoring force, to an accommodation position. The shaft comprises a flexible membrane wall providing a seal between the outer and central portions that flexes to accommodate the relative axial movement between them. Preferably the membrane wall is itself elastic or elastomeric to provide all or some of the restoring force as it flexes to the displacement position. Preferably a mechanical spring, conveniently a helical spring, is provided acting between the two shaft components to urge them back towards the accommodation position. The membrane wall may be at the shaft""s end face and be continuous across the central portion thereof, so that the only fluid-tight join needed is that to the outer annular shaft portion. Action on the central end portion from the plunger head is preferably mechanical action via a stem component of the shaft extendingxe2x80x94preferably continuously but optionally with lost motion or other discontinuityxe2x80x94from the head to the inner end centre of the shaft. Action via compression of an enclosed air space would also be possible. Where the membrane wall is continuous across the inner end, the end of a mentioned stem component can act on the rear face of the membrane wall.
The outer shaft portion may be a rigid ring piston mounting an outwardly-directed resilient sealing element to contact the cylinder wall and also having a joint arrangement for connecting the periphery of the flexible membrane wall.
Preferably rigid mechanical limit stop engagements are provided acting between the axially relatively-movable components of the shaft to protect the membrane wall against excessive deformations. A central stem component as mentioned preferably makes a guiding or centering engagement with the outer annular portion.
When the user presses the plunger down the central end portion advances to its displacement position, i.e. the end of the plunger occupies a relatively larger volume within the pump cylinder. When pressure on the plunger is released at the end of the dispensing strokexe2x80x94which need not be a complete strokexe2x80x94the plunger""s central end portion retracts under the restoring force so that for a given position of the primary seal the volume displaced by the piston is then reduced. This reduction in displacement by the piston at the end of a dispensing stroke can be exploited to accommodate material sucked back into the pump chamber in accordance with the first proposals above. However the second proposals have independent significance beyond the first proposals. For example the reduction in piston displacement at the end of the dispensing stroke can be used to drive a suck-back phenomenon, by creating negative pressure in the pump chamber, in cases where the outlet valve is adapted for suck-back in some way other than in the first proposal e.g. by manufactured imperfection or by delayed closure.
Furthermore the ability to modify the piston displacement without sliding the primary seal may provide a desirable auxiliary dispensing function whereby small movements of the dispenser head can be used to dispense small volumes corresponding to the change in plunger displacement without sliding the primary seal. This can provide xe2x80x9cspot dosesxe2x80x9d in a reproducible way which would be hard to do consistently by bodily movement of the plunger.
This spot-dosing function may be exploited in a dispenser pump of the kind described without any suck-back arrangement, if wished.
A third set of proposals herein relates to dispenser pumps of the kind described having a projecting discharge nozzle whose nozzle tip has a downwardly-directly directed end opening, and in which pump a suck-back arrangement (preferably but not essentially in accordance with the first set of proposals above) is provided for drawing product residues upstream towards the pump chamber along a main discharge passage of the nozzle. In our proposals the nozzle tip has at least one longitudinal internal dividing wall which divides the discharge passage into passage portions extending side by side. At least one of these passage portions is open while at least one other is obstructed at or adjacent the end opening by a displaceable closure flap, e.g. a resiliently deformable flap valve.
Preferably a said internal dividing wall is a central conduit which defines a central, open passage portion surrounded by an annular passage region closable by an annular displaceable closure flap.
The purpose of this subdivision is to improve the effectiveness of suck-back, particularly in nozzles made with relatively large cross-section to reduce the effort of dispensing. During dispensing the closure flap is displaced outwardly by the flow of liquid product, so that a large nozzle area is exploited. When flow ceases the flap then returnsxe2x80x94preferably resilientlyxe2x80x94to block the respective passage portion so that the ensuing reverse flow caused by the suck-back is concentrated in the open passage portion. The suck-back then acts more effectively to clear the proportionately smaller passage, while the closure flap and dividing wall inhibit dripping of liquid from the other passage portion(s).
Preferably the discharge nozzle inclines upwardly from the outlet except adjacent the nozzle tip where the mentioned subdivision is provided. Provided that the suck-back can clear the open passage portion(s) back into the inclined nozzle portion, dripping can effectively be prevented. The inclined arrangement also avoids excessive accumulation of liquid behind the closure flap.
A fourth set of proposals herein relates to dispenser pumps of the kind described in which the plunger is a piston axially reciprocable in a cylinder formed by the body of the pump, between innermost and extended limit positions corresponding to a full dose, and has a shaft passing through top guide portion of the pump body. The pump body""s guide portion has a click formation engageable with a click formation on an intermediate portion of the piston shaft to give a sensible e.g. audible and/or tangible user signal corresponding to a predetermined part-dose plunger position as the shaft""s intermediate portion moves through the guide portion.
This user signal may be exploited when raising the plunger in a hand-primed pump, so as to fill the chamber only partially but to a predetermined extent. Or, the fully-primed chamber may be only partially emptied to a predetermined extent by depressing the plunger until the is signal is noted.
The piston shaft may have more than one click formation at spaced positions corresponding to part-doses of different sizes.
Preferably the piston shaft, which is usually cylindrical, has an axially-extending circumferentially-localised channel in which a shaft click projection is recessed so as not to project beyond the surface envelope of the shaft. Correspondingly a click projection on the body""s guide portion projects into the channel on the shaft to interfere with the click projection therein as it passes. Preferably the or each shaft click projection is a rigid lug while the guide portion""s click projection may be another rigid lug or more preferably a flexible tongue. An alternative click formation would be an axially-localised recess on one of the components, preferably the shaft, to engage a projection on the other.
A click projection for the guide portion may conveniently be provided on a discrete annular fitting securable to the guide portion, for ease of manufacture.
The plunger stem may carry distinctive visual symbols representative of dose sizes which appear immediately above the body at click positions.
As will be appreciated from the discussion herein and the ensuing description of embodiments, the above independent proposals can be freely combined.
We particularly envisage their implementation in pumps with relatively large dose sizes, say from 50 ml upwards. Preferably the plunger is arranged for generally upright operation. The pump may be manually-primed, i.e. without a return spring, to reduce the dispensing force required since various of the above proposals are useful to this end. Means for connecting the pump to a supply container may position the container beside or above the pump so that there is a positive fluid pressure at the pump inlet. The nature of the pump inlet is not particularly limited. A flap valve is preferred for the inlet valve because of its low operating force, but other kinds of valve may be used.
A fifth independent proposal hereinxe2x80x94again, freely combinable with all of the other proposals hereinxe2x80x94relates to the construction of a connecting conduit bridging between a fluid supply outlet and a pump inlet in a dispensing system, where the outlet and inlet both extend transversely to the bridging direction e.g. with pump and supply side-by-side, their respective inlet and outlet directed downwardly. A conventional U-tube has multiple components and is hard to dismantle. Our proposal is to form the conduit from two shell portions which face one another in the mentioned transverse direction and are joined around a single loop of boundary joint, preferably substantially in one plane. A first one of the shell portions has first and second tubular formations, spaced in the bridging direction, for the fluid supply outlet and pump inlet respectively. At least one of the shell portions, preferably at least and most preferably only the first one, has an open bridging recess extending in the bridging direction which, when the shell portions are joined together around the boundary, provides an enclosed bridging conduit section connecting the fluid supply tube to the pump inlet tube.
This proposal advantageously enables easy manufacture of the parts, since both tubular formations can extend in a mould-separation direction for moulding the first shell portion. The second shell portion is preferably a substantially flat plate. If wished, the pump inlet union tube may be formed in one piece with a pump cylinder wall of the pump.